chore: Enhance FileSession batching reliability and error clarity

[prmukherj]

Context

FileSession batching behavior had several issues: scalar field requests incorrectly reflected node/boundary semantics that don't apply to file-based sessions, batch responses overwrote prior results when multiple requests targeted the same surface, and public docstrings misled callers about node_value/boundary_value behavior.

Change Summary

• Scalar option normalization: node_value/boundary_value are normalized to False for FileSession scalar reads (face/element-only), emitting a PyFluentDeprecationWarning with correct stacklevel when non-default values are passed.
• Consistent enum usage: DataLocation enum used in both tag construction and response aggregation, eliminating fragile integer-to-enum key alignment.
• _ScalarFieldTransaction defaults: node_value/boundary_value now default to False, accurately reflecting FileSession semantics regardless of instantiation path.
• Batch response merging: Switched to setdefault-based aggregation so multiple scalar/vector field requests for the same surface merge instead of overwriting.
• Selective mesh reads: Batch.get_response now respects provide_faces/provide_vertices flags, skipping unnecessary connectivity/vertex reads for surfaces that didn't request them.
• Docstrings: Updated add_scalar_fields_request and get_scalar_field_data to document that node_value/boundary_value are ignored in FileSession (face-only data) and emit a deprecation warning when set to True.

Rationale

FileSession reads data from files (face/element only); exposing node/boundary options as meaningful controls is incorrect and misleading. Merging rather than overwriting batch results is necessary for correctness when multiple field requests share a surface.

Impact

• FileSession scalar field batching and direct reads.
• Callers passing node_value=True or boundary_value=True will now see a deprecation warning.
• Batch responses for multi-request scenarios will no longer silently drop earlier results.

[Copilot]

Pull request overview

This PR tidies up FileSession batching behavior so that batched field-data requests correctly normalize FileSession-only scalar semantics and merge multiple requests for the same surface without overwriting prior results.

Changes:

• Added scalar option normalization for FileSession scalar reads (node/boundary options normalized to face/element semantics with a deprecation warning).
• Updated batch response aggregation to merge multiple scalar/vector fields and surface data per surface via setdefault (instead of overwriting).
• Added tests to validate scalar request option handling and per-surface merging behavior in batch responses.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
tests/test_file_session.py	Adds regression tests covering scalar option normalization behavior and per-surface merging in batch responses.
src/ansys/fluent/core/file_session.py	Normalizes scalar request options for FileSession, improves batch aggregation merging, and tightens vector field name validation.

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[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

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[seanpearsonuk]

@prmukherj I notice that Copilot used "tidies up" in its PR summary, but it writes "tidies up FileSession batching behavior," whereas titling the PR chore: Tidy up File Session gives a false impression that the PR does not include any behavioural changes. This becomes a problem when we read the logs later. It would be better to emphasise in the title that this PR is all about fixes.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

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